CN115951446A - Polarization maintaining optical fiber with rectangular fiber core cross section and manufacturing method thereof - Google Patents

Abstract

The invention discloses a polarization maintaining optical fiber with a rectangular fiber core cross section and a manufacturing method thereof, which solve the problem that a high stress type optical fiber stress area is easy to break during grinding, improve the long-term reliability of the optical fiber and improve the temperature characteristic of a related optical fiber sensor.

Description

Polarization maintaining optical fiber with rectangular fiber core cross section and manufacturing method thereof

Technical Field

The application relates to the field of polarization maintaining optical fibers, in particular to a polarization maintaining optical fiber with a rectangular fiber core cross section and a manufacturing method thereof.

Background

The polarization maintaining optical fiber is used as a special optical fiber and widely applied to various fields of national economy such as aerospace, aviation, navigation, industrial manufacturing technology, communication and the like. In an interference type optical fiber sensor based on optical coherent detection, the polarization maintaining optical fiber is used to ensure that the linear polarization direction is unchanged, and the coherent signal-to-noise ratio is improved, so that high-precision measurement of physical quantity is realized.

Specifically, the polarization maintaining fiber is further classified into a panda fiber, a bow-tie fiber, an elliptical cladding fiber, and an elliptical core fiber. The first three are typical stress-type polarization maintaining fibers, and the last one belongs to a polarization maintaining fiber based on geometric birefringence, but because the beat length is generally larger than 8 mm, the beat length is difficult to be made smaller than 3.5 mm, even smaller than 2 mm like the stress-type fiber. This is limited by the structure of the elliptical core.

Although the polarization maintaining performance of the stress type polarization maintaining optical fiber is better as the beat length is shorter, the biggest problems are that the optical fiber is more fragile, and particularly, the breakage is more likely to occur when the radius of curvature is relatively small, and such an optical fiber is not suitable for end grinding and the stress region is easily broken. And their corresponding sensor temperature characteristics may also deteriorate. The phenomenon is particularly obvious when the optical fiber gyroscope and the optical fiber current sensor are researched and produced. If the ordinary panda structure optical fiber is adopted to make the current sensing optical fiber, the temperature dependence of the whole temperature exceeds 3 percent, and the temperature dependence of the improved stress type optical fiber is still about 2 percent.

Disclosure of Invention

In order to solve the problem that an optical fiber in a high stress area is easy to break and improve the temperature characteristic of a related optical fiber sensor on the premise of ensuring the polarization maintaining performance, the application provides a polarization maintaining optical fiber with a rectangular fiber core cross section and a manufacturing method thereof. Such optical fibers achieve polarization-maintaining properties through their form birefringence.

The application provides a polarization maintaining optical fiber with a rectangular fiber core cross section, which adopts the following technical scheme:

a polarization maintaining optical fiber with a rectangular fiber core cross section comprises a rectangular fiber core and a pure quartz rod, wherein a placement hole is formed in the center of the pure quartz rod, and the rectangular rod core is located in the placement hole; the cross section of the rectangular fiber core is of a rectangular structure and is embedded in the placement hole, and the shape of the cross section of the placement hole is the same as that of the cross section of the rectangular fiber core in shape and size.

Preferably, the rectangular core has a long side and a short side, and the ratio of the long side to the short side is 2 to 5.

A method for manufacturing a polarization maintaining optical fiber with a rectangular cross section comprises the following steps:

taking a first pure quartz rod with the diameter of 40mm and the length of 400mm, and drilling a through hole with the diameter of 8-10 mm along the longitudinal direction of the first pure quartz rod at the center of the cross section of the first pure quartz rod;

step two: then a second pure quartz rod with the diameter of 40mm and the length of 400mm is taken, a rectangular through hole is drilled in the center of the cross section of the second pure quartz rod along the longitudinal direction of the second pure quartz rod, and the ratio of the long side to the short side of the rectangular hole is 2-5;

step three: taking a prefabricated rod of a 105/125um multimode optical fiber, grinding the prefabricated rod into a rectangular cross section in a lateral grinding mode to prepare a rectangular fiber core, wherein the width and the length of the prefabricated rod are consistent with the width of a wide rectangular hole;

step four: inserting the ground prefabricated rod into the rectangular hole, and simultaneously reducing the diameter of the second pure quartz rod by using optical fiber prefabricated rod extension equipment to enable the diameter of the second pure quartz rod to be consistent with the diameter of the through hole;

step five: and inserting a second pure quartz rod into the through hole, and drawing the second pure quartz rod into a finished optical fiber product.

In summary, the present application includes at least one of the following beneficial technical effects:

one is as follows: the birefringence of the invention is 3 to 4 times larger than that of the traditional elliptical core fiber, and the polarization maintaining capability of the fiber without the stress area is improved.

The second step is as follows: the shape of the traditional elliptical core optical fiber is changed, sharp corners at two ends are eliminated, the structural characteristics at two ends of the rectangular fiber core are fully utilized, the stress region is eliminated, and the temperature characteristic of a related sensor is improved.

And the third step: avoid the stress region of the stress type optical fiber from cracking due to long-term bending and avoid the stress region from cracking due to grinding.

Drawings

FIG. 1 is a schematic structural diagram of a polarization maintaining fiber with a rectangular core cross section according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a rectangular core structure disclosed in an embodiment of the present application;

fig. 3 is a refractive index profile of a polarization maintaining fiber with a rectangular core cross section according to an embodiment of the present application.

Description of reference numerals: 12. a rectangular core; 2. a pure quartz rod; 3. placing the hole; 5. an arc-shaped surface.

Detailed description of the preferred embodiments

The present application is described in further detail below with reference to the attached drawings.

The embodiment of the application discloses a polarization maintaining optical fiber with a rectangular fiber core cross section.

Referring to fig. 1-3, a polarization maintaining fiber with a rectangular fiber core cross section, the preform rod of which mainly comprises a rectangular fiber core 12 and a pure silica rod 2, a placement hole 3 is formed in the center of the pure silica rod 2, and the rectangular fiber core 12 is positioned in the placement hole 3.

Specifically, in the processing process, the present embodiment includes a rod core (also made of pure quartz, and after being drawn, the rod core is integrated with the pure quartz rod 2, so that the drawing is not separately shown) and a rectangular fiber core 12, and the rod core 12 is used for prefabricating and installing the rectangular fiber core 12. The cross section of the rectangular core 12 is designed to be rectangular and finally embedded in the pure silica rod 2, and therefore, the cross section of the placement hole 3 needs to be the same as the cross section and size of the rectangular core 12.

To further improve the performance of this embodiment, the rectangular core 12 is further modified. Since the rectangular core 12 has long and short sides, the present embodiment defines a ratio of long to wide, which is between 2 and 5. In combination with the shape of the rectangular core 12 in the present embodiment, the birefringence is 3 to 4 times greater than that of the elliptical core fiber when the aspect ratio is the same as the ratio of the major axis to the minor axis of the conventional elliptical core fiber.

Then, the present embodiment also has slightly recessed arc-shaped faces 5 on two sides of the rectangular core 12, and the corners of the long side and the short side are rounded, similar to a dumbbell shape, to obtain a higher birefringence effect.

The manufacturing method of the embodiment comprises the following steps:

taking a first pure quartz rod with the diameter of 40mm and the length of 400mm, and drilling a through hole with the diameter of 8-10 mm along the longitudinal direction of the first pure quartz rod at the center of the cross section of the first pure quartz rod;

step two: then a second pure quartz rod with the diameter of 40mm and the length of 400mm is taken, a rectangular through hole is drilled in the center of the cross section of the second pure quartz rod along the longitudinal direction of the second pure quartz rod, and the ratio of the long side to the short side of the rectangular hole is 2-5;

step three: taking a prefabricated bar (generally, the cross section is circular) of a 105/125um multimode optical fiber, grinding the prefabricated bar into a rectangular cross section in a lateral grinding mode to prepare a rectangular fiber core 12, wherein the width and the length of the prefabricated bar are consistent with the width of a wide rectangular hole;

step four: inserting the ground prefabricated rod into the rectangular hole, and simultaneously reducing the diameter of the second pure quartz rod by using optical fiber prefabricated rod extension equipment to enable the diameter of the second pure quartz rod to be consistent with the diameter of the through hole;

step five: and inserting a second pure quartz rod into the through hole, and drawing the fiber into a finished optical fiber product according to the drawing process flow.

Preliminary results have shown that: the temperature dependence of the rectangular core polarization maintaining optical fiber is hopefully inhibited to be within 1 percent.

The above are preferred embodiments of the present application, and the scope of protection of the present application is not limited thereto, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (3)

1. A polarization maintaining fiber with a rectangular fiber core cross section is characterized in that: the fiber-reinforced composite material comprises a rectangular fiber core (12) and a pure quartz rod (2), wherein a placement hole (3) is formed in the center of the pure quartz rod (2), and the rectangular fiber core is positioned in the placement hole (3); the cross section of the rectangular fiber core (12) is of a rectangular structure and is embedded in the placement hole (3), and the cross section of the placement hole (3) is the same as that and size of the rectangular fiber core (12).

2. A polarization maintaining optical fiber having a rectangular core cross-section as claimed in claim 1, wherein: the rectangular fiber core (12) has a long side and a short side, and the ratio of the long side to the short side is 2 to 5.

3. A method of manufacturing a rectangular-section polarization maintaining optical fiber according to any one of claims 1 to 2, characterized in that: the method comprises the following steps:

taking a first pure quartz rod with the diameter of 40mm and the length of 400mm, and drilling a through hole with the diameter of 8-10 mm along the longitudinal direction of the first pure quartz rod at the center of the cross section of the first pure quartz rod;

step two: then a second pure quartz rod with the diameter of 40mm and the length of 400mm is taken, a rectangular through hole is drilled in the center of the cross section of the second pure quartz rod along the longitudinal direction of the second pure quartz rod, and the ratio of the long side to the short side of the rectangular hole is 2-5;

step three: taking a prefabricated rod of a 105/125um multimode optical fiber, grinding the prefabricated rod into a rectangular cross section in a lateral grinding mode to prepare a rectangular fiber core (12), wherein the width and the length of the prefabricated rod are consistent with those of a rectangular hole;

step four: inserting the ground prefabricated rod into the rectangular hole, and simultaneously reducing the diameter of the second pure quartz rod by using optical fiber prefabricated rod extension equipment to enable the diameter of the second pure quartz rod to be consistent with the diameter of the through hole;

step five: and inserting a second pure quartz rod into the through hole, and drawing the second pure quartz rod into a finished optical fiber product.

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